Mobile device and methods for travelling towards a destination using a communication network

This application is a 35 U.S.C. § 371 national stage application of PCT International Application No. PCT/IN2020/050087 filed on Jan. 27, 2020, which in turn claims foreign priority to Indian Patent Application number 201911030345, filed on Jul. 26, 2019, the disclosures and content of which are incorporated by reference herein in their entirety.

Embodiments herein relate to a method and mobile device in a communications network. In particular, embodiments herein relate to travelling towards a destination using the communications network.

Path planning is a critical enabling technology for mobile devices to be truly autonomous. Mobile devices, when used herein, include mobile agents, vehicles, aerial vehicles and similar. Mobile device path planning can be done in various ways taking into account constraints in the 3D-space and known obstacles. Such algorithms take a spatial map along with obstacle maps as input, which can be very large in size, and therefore is typically compute intensive.

Therefore, path planning may be done globally for a given mission, with a given initial and goal state and a representation of the environment. Because of the compute intensive nature of such algorithms, path planning is usually done offline prior to flight, in the Cloud (and not in the mobile device). The paths thus found are collision-free with regards to known obstacles which are known a priori, such as buildings, trees etc.

However, during travel or flight, dynamic restricted zones, no-fly zones or dynamic obstacles may arise. Such scenarios require re-planning of the path or planning a new path. The cloud-based path planning may not be accessible if the mobile device faces such hazards in zones with low connectivity or no connectivity, since there would be no way of communicating data of the obstacles to the mobile device and/or for the mobile device to get guidance about re-planned waypoints.

Since mobile device path planning must consider zones or areas with different connectivity qualities, it is essential to have a path planning system that ensures a path for the mobile device at any point of its flight, regardless of unforeseen obstacles.

Path planners, in the most basic sense, may first build an environment perception, such as a map, graph or tree of all feasible branches. In deterministic methods, the map is primarily built in a systematic, exhaustive way. In sampling-based methods, the map is built by sampling randomly and adding the samples to the map if reachable, i.e. if the path is collision-free.

Once the map is built, the second step is to query the map with a given initial state and a given goal state, i.e. a present location and a destination location. The path is found by a search to find a possible path, also referred to as a feasible path, if it exists. This path is input to the mobile device, and the mobile device follows the path using its automatic controlling system, such as an autopilot, and on-board controllers. Thus, it is generally considered that the process of providing autonomy occurs in the cloud, while the execution control at the mobile device is non-autonomous and only follows the path that is given to the mobile device.

As a part of developing embodiments herein, the inventors identified a problem which will first be discussed.

As mentioned above, in current solutions, path planning is done globally. The global planning is then followed by local path-following control. This assumes access to complete information at the time of planning, and very little deviation in the environment at the time of travel. Some solutions propose local control via communication with the cloud, which assumes perfect connectivity. However, assuming perfect connectivity may not be realistic, particularly in safety-critical applications such as mobile device flight applications.

When mobile device paths must pass through zones with different degrees of connectivity, one way to handle unexpected obstacles in a zone with insufficient connectivity is to trace back to a previous zone with adequate connectivity, communicate the observed obstacle details, such as position and extent, to the cloud and obtain a new path. However, this may not be a good solution for energy-constrained mobile devices.

One way to ensure availability of paths at all time is by letting the mobile device have the entire map of a region in its memory and let the mobile device compute a new path, i.e. perform re-planning, in cases of unexpected obstacles, thus taking over path planning locally in case of insufficient connectivity. However, this is not feasible in most cases, due to severe constraints on memory and compute cycles in the mobile devices, to be dedicated for re-planning. The required data may e.g. occupy hundreds of MBs or GBs in the memory of a mobile device. Such a large input data occupancy may, furthermore, not be feasible since a large part of the memory typically needs to be dedicated for a task to be performed by the mobile device, such as recording a video feed.

Storing the entire environment graph or roadmap onboard a mobile device is thus not preferred. In a typical case, only the planned path is stored on board, and a control loop may be closed via a controller in the cloud. Such schemes may however be highly problematic, especially in cases where: a true environment deviates from the planned environment, e.g. if a new obstacle exists then a new path plan is required, the mobile device may lose connectivity, and may therefore only rely on its own knowledge of the path; and where the mobile device encounters a changed environment and loses connectivity with the cloud. In the latter scenario, dangerous situations may occur, leading to a mobile device with no means to achieve its mission, which may potentially lead to loss of life or property. Such an event may be referred to as a deadlock.

An object of embodiments herein is, therefore, to improve the performance of a mobile device travelling towards a destination using a communication network.

According to an aspect of embodiments herein, the object is achieved by a method performed by a mobile device such as an aerial vehicle for travelling towards a destination using a communication network. The mobile device obtains from one or more network nodes in the communication network, a first path over a first sub-region of a region towards the destination. The mobile device further follows the first path; and upon entering, or being in, a second sub-region of the region having a level of connectivity below a threshold, the mobile device switches to follow a second path calculated locally at the mobile device.

According to a further aspect of embodiments herein, the object is achieved by providing a mobile device for travelling towards a destination using a communication network. The mobile device is configured to obtain from one or more network nodes in the communication network, a first path over a first sub-region of a region towards the destination, and to follow the first path. The mobile device is further configured to, upon entering or being in a second sub-region of the region having a level of connectivity below a threshold, switch to follow a second path calculated locally at the mobile device.

The performance of the mobile device travelling towards a destination may be improved according to the embodiments herein. In such an approach, safety of the mobile device may be ensured at all times since the mobile device always has a path where obstacles are taken into account. Such an approach may comprise a mobile device and a process between the mobile device and one or more network nodes, e.g. a cloud server, that consider variability of connectivity along a route while ensuring that the mobile device has access to a path to the destination all the time, so far as allowable by a regional map.

Embodiments herein thus provide a mobile device and method to manage the location of autonomy in path planning.

is a schematic overview depicting a communications networkwherein embodiments herein may be implemented. The communications networkcomprises one or more Radio Access Networks (RANs) and one or more Core Network (CNs). The communications networkmay use any technology such as 5G new radio (NR) but may further use a number of other different technologies, such as, Wi-Fi, long term evolution (LTE), LTE-Advanced, wideband code division multiple access (WCDMA), global system for mobile communications/enhanced data rate for GSM evolution (GSM/EDGE), worldwide interoperability for microwave access (WiMax), or ultra mobile broadband (UMB), just to mention a few possible implementations.

Mobile devices, such as a mobile device, operate in the communications network. The mobile devicemay be any device moving within the communications network such as a mobile agent e.g. a vehicle such as an aerial vehicle and/or an unmanned vehicle. The mobile devicemay e.g. be a mobile station, a non-access point (non-AP) STAtion (STA), an STA, a user equipment (UE) and/or a wireless terminal, an NB-internet of things (IoT) mobile device, a Wi-Fi mobile device, an LTE mobile device and an NR mobile device communicating via one or more Access Networks (AN), e.g. RAN, to one or more core networks (CN). It should be understood by those skilled in the art that “mobile device” is a non-limiting term which means any terminal, wireless communication terminal, wireless mobile device, device to device (D2D) terminal, or node e.g. smart phone, laptop, mobile phone, sensor, relay, mobile tablet, television unit or even a small base station communicating within a cell. The methods according to embodiments herein are performed by the mobile device.

Network nodesoperate in the communications network. Such a network node may be a cloud based server or an application server providing processing capacity for e.g. calculating paths or similar along a route to a destination for the mobile device. The communications networkmay further comprise one or more radio network nodesproviding radio coverage over a respective geographical area by means of antennas or similar. The geographical area may be referred to as a cell, a service area, beam or a group of beams. The radio network nodemay be a transmission and reception point e.g. a radio access network node such as a base station, e.g. a radio base station such as a NodeB, an evolved Node B (eNB, eNode B), an NR Node B (gNB), a base transceiver station, a radio remote unit, an Access Point Base Station, a base station router, a transmission arrangement of a radio base station, a stand-alone access point, a Wireless Local Area Network (WLAN) access point, an Access Point Station (AP STA), an access controller, a UE acting as an access point or a peer in a Mobile device to Mobile device (D2D) communication, or any other network unit capable of communicating with a UE within the cell served by the radio network nodedepending e.g. on the radio access technology and terminology used.

Embodiments herein relate to allowing path planning of the mobile deviceto be carried out both globally in the communications network and locally on-board the mobile deviceby e.g. switching intelligently between the paths so as to assure safety of the mobile deviceat all times. Safety of the mobile device, when used herein, may refer to that the mobile device has a safe path to a next high-connectivity region.

An advantage of embodiments herein is that path planning autonomy may be distributed intelligently between the one or more network nodesand the mobile device. Further advantages of embodiments herein may be achieved through the enhanced execution protocol provided, which switches between global path planning, i.e. network nodecontrolled, and local path planning, i.e. mobile devicecontrolled, for a safe graph construction. An efficient use of embodiments herein may further be achieved through adaptive computation of safe graphs or safe subgraphs with density, which density may be dynamically calculated by taking resource constraints onboard the mobile device into account. Such resource restraints may e.g. be restraints on mobile devicememory, computation capability, battery, and time availability for download. Thus, usage of dynamic generation of safe subgraphs with adaptive density may achieve an efficient use. Another advantage of embodiments herein is that they provide an added value, since services using the proposed mobile deviceand method may extend the applicability of 5G-based solutions to mobile device use cases depending on path planning. This will improve mobile deviceservice providers adopting 5G-based services.

Embodiments herein use a region that is partitioned into sub-regions being associated with a level of connectivity. Thus, some embodiments herein relate to partitioning a region into sub-regions of connectivity zones, i.e. partition a region within which a path is to be found from a source, e.g. the present location, to a destination. Each sub-region has an assigned level of connectivity, e.g. 0 or 1 wherein ‘0’ is used to denote a sub-region with no or otherwise inadequate connectivity, and ‘1’ is used to denote full or otherwise adequate connectivity. Sub-regions may thus also be referred to as connectivity zones.

In some embodiments herein, a solution is provided that comprises a protocol for switching between the local path planning, performed in the mobile device's processor, and global path planning, performed elsewhere in the communications network. This protocol may be divided in two phases: phase 1 and phase 2. When employing the phase 1 protocol, the mobile deviceis in a 1-connectivity zone, meaning that the connectivity is full or otherwise adequate. In such a connectivity zone, the mobile devicefollows a first path. If there is an obstacle, the mobile devicecommunicates with one or more network nodesin the communications networkto get a different path and a subgraph for the subsequent sub-region with no or otherwise inadequate connectivity, herein referred to as 0-connectivity zone. The path which the mobile devicefollows through the 1-connectivity zone may ideally be such that the mobile devicehas sufficient time to download the required subgraph. At the boundary point, which is the entry point to the 0-connectivity zone, the mobile devicefollows the phase 2 protocol.

When employing the phase 2 protocol, the mobile deviceis in a boundary point or in a 0-connectivity zone. Under such conditions, the mobile devicere-plans its path locally to reach a boundary point, which is an entry point to the subsequent sub-region i.e. a 1-connectivity zone. At the boundary point, the mobile devicecommunicates with the one or more network nodesto get a next safe subgraph downloaded. The mobile devicemay wait at the boundary point, e.g. by hovering, until the safe subgraph has been downloaded. When the safe subgraph has been downloaded, the mobile device follows the phase 1 protocol.

At each point in the path from a starting point to the destination, the mobile device may maintain a subgraph of the entire map such that:

When used herein, a fully dense map may refer to a map comprising as much map data input as possible, i.e. comprising all accessible information of map data such as roads, buildings, obstacles, zones of restrictions or other important information for route planning. Furthermore, when used herein, boundary points refer to points on the boundary between sub-regions and may be said to represent gateways leading to 1-connectivity zones. A subgraph fulfilling the requirements (1)-(3) above is referred to as a safe subgraph.

An advantage of embodiments herein is that an ability for the mobile device to plan autonomously when required is provided. Since the employed subgraph is safe in every point during the flight of the mobile device, the mobile deviceis never orphaned. This means that the mobile devicenever reaches a situation where the mobile device is in an inadequate connectivity zone and/or without a map with which to re-plan the path locally.

Further advantages of embodiments herein comprise reduced strain on memory and computation capability, since the subgraph may be a small portion of an entire map.

depict the alternating phases of the protocol by means of an example scenario where the mobile devicetravels from a starting point S, also referred to as an initial location, to the destination point D, also referred to as a goal location, over a region. The mobile devicethereby crosses a plurality of sub-regions of the region, which sub-regions may also be referred to as zones. The sub-regions may differ in connectivity, where C=1 indicates a sub-region with adequate connectivity and C=0 indicates a sub-region with inadequate connectivity. In, two maps are shown, where the top-most map shows one or more possible paths the mobile devicemay take, and the lower-most map shows the outcome trajectory of the mobile devicein the example scenario.

In, the corresponding connectivity levels of the sub-regions are indicated by the graph below the maps.is an annotated version of the lower-most map in FIG.. As mentioned above, in the example scenario depicted in both, the mobile deviceis tasked with travelling from the initial location to the destination. As can be seen in the figures, the initial point is located at point S in the sub-region Z, and the destination is located at point D, in the sub-region Z+4.

Thus, the mobile devicebegins its journey at S in the sub-region Z, which is a sub-region with a connectivity level equal to or above a threshold, e.g. a C=1 sub-region, and thus, the mobile devicemay continue along a single path, also referred to as the first path, see action.

In the sub-region Z+1, subsequent to the sub-region Z, however, the level of connectivity is below the threshold, e.g. a C=0 sub-region. In the sub-region Z+1 the connectivity is inadequate for the purpose of controlling the mobile devicevia the network nodesand therefore, the mobile devicemay need to cross the sub-region Z+1 independently. This means that the phase 2 protocol may be employed in the Z+1 sub-region, see action. In order for the mobile deviceto be able to follow the phase 2 protocol however, one or more possible second maps or possible paths may be downloaded to the mobile devicein the first sub-region Z, see action. The one or more second paths may also be referred to as one or more second safe subgraphs. The network nodecalculated possible paths may be downloaded to the mobile devicebefore the mobile deviceenters the Z+1 sub-region, since there will be inadequate connectivity in that sub-region. Therefore, during the crossing of the Z sub-region for example, the one or more paths covering the sub-region Z+1 may be downloaded to the mobile device.

Using the one or more downloaded second paths, a path through the Z+1 sub-region may be determined and followed see action. In, this path is referred to as a possible path. An objective of determining a possible path is to find a suitable path to a boundary point on the edge between the sub-region Z+1 and the subsequent sub-region, Z+2. Examples of calculated paths from the boundary between Z and Z+1 to the boundary between Z+1 and Z+2 are illustrated with dashed lines in. These dashed lines all lead to exemplified boundary points.

When the mobile deviceencounters an obstacle in the zone Z+1, it cannot rely on a functionality in the communication networkto re-plan the path through the sub-region Z+1. Since there is inadequate connectivity in the sub-region Z+1, the mobile devicelocally calculates a second path independently of the one or more network nodes, e.g. upon detecting an obstacle, see action. In such a scenario, the mobile deviceis capable of recalculating the second path. It should be noted that if the mobile deviceis unable to recalculate a second path through the second sub-region Z+1, the mobile devicemay retrace its journey back to the boundary between the sub-regions Z and Z+1, which is a last known location where the mobile devicehad an adequate connection to the communication network, and either retrieve alternate paths or select an alternate path. The mobile devicemay then return to the boundary between the sub-regions Z and Z+1, since it was unable to calculate a second path upon encountering an obstacle on the shortest path from the boundary point on the sub-region Z to the boundary point on the sub-region Z+2. At the boundary, the mobile devicereceives a new path on which to traverse the sub-region Z+1.

According to the illustrated example the mobile devicefollows the second path to the third sub-region Z+2, see action. Having successfully traversed the second sub-region Z+1 by means of the calculated second path, the mobile deviceenters a third sub-region Z+2. The sub-region Z+2 is a sub-region with a level of connectivity above or equal to the threshold, e.g. C=1 sub-region, so the mobile devicemay again switch to the phase 1 protocol and be controlled by functionality in the communications networkand, thus, it may follow a single path through the sub-region Z+2, see actions-. In, this path is referred to as the third path. If the mobile deviceencounters an obstacle in the Z+2 sub-region, it communicates with the one or more network nodesto get a different path. The mobile devicemay also communicate with the one or more network nodesto require one or more possible paths for a subsequent sub-region Z+3 i.e. a fourth sub-region, which may e.g. be a C=0 sub-region. These possible paths may be downloaded to the mobile device, see action.

At the boundary point of the sub-regions Z+2 and Z+3, which is an entry point into the fourth sub-region Z+3, the mobile devicemay again switch to use the phase 2 protocol, see action. In accordance with the phase 2 protocol, the mobile devicemay follow a possible path downloaded previously, see action, and the mobile device may calculate a fourth path to a boundary point on the edge between the sub-regions Z+3 and Z+4, e.g. upon detection of a change of a parameter, such as a value from a sensor or a measurement of signaling quality, being associated with describing an environment of the fourth sub-region such as parameter indicating a detection of an obstacle, see action. Therefore, the mobile devicedoes not need to return to the boundary with the previous sub-region, Z+2 for connecting to the cloud. In, this path is referred to as the new fourth path, and the mobile devicefollows the fourth path, see action.

Having reached a boundary point on the edge between the sub-regions Z+3 and Z+4, the mobile devicecommunicates with the one or more network nodesto get a next safe subgraph, i.e. a safe path through the fifth sub-region Z+4, downloaded. In the example scenario, the mobile device's destination point D is located in the sub-region Z+4 and thus it requests, from the one or more network nodes, a path to the destination point D. In, this path is referred to as the fifth path.

When the safe subgraph, or map, comprising the path has been downloaded, the mobile devicefollows the phase 1 protocol. Unless it encounters obstacles and must re-plan the route towards the destination, the mobile devicefollows the downloaded path and consequently reaches its destination, see action. A density of the downloaded safe subgraphs comprising the various possible paths may be based on the available resources in the mobile deviceand/or the communications network, which will be discussed more in detail below.

Example embodiments of a method performed by the mobile devicefor travelling towards a destination using the communication networkwill now be described with reference to a flowchart depicted in. The mobile devicemay be represented by any mobile agent such as e.g. an aerial vehicle and/or an unmanned vehicle. The method comprises the following actions, which actions may be taken in any suitable order. Actions that are optional are presented in dashed boxes in.

Action. In an example scenario herein, the mobile devicemay collect, internally and/or externally of the mobile device, information regarding the level of connectivity in the region. This information may e.g. be retrieved from a network nodeor a database. The mobile devicemay in some scenarios locally perform measurements and collect information of level of connectivity.

Action. The mobile devicemay further partition the region into sub-regions based on the level of connectivity. The region may thus be partitioned into at least the first and the second sub-region.

Action. The mobile deviceobtains, from the one or more network nodesin the communication network, the first path over the first sub-region of the region towards the destination. The region may comprise more than one sub-region.

Action. The mobile devicefollows the obtained first path.

Action. Upon entering or being in the second sub-region of the region, wherein the second sub-region has a level of connectivity below a threshold, the mobile deviceswitches to follow a second path towards the destination, calculated locally at the mobile device. E.g. upon detection of a change of a parameter being associated with describing an environment of the second sub-region e.g. detecting an obstacle, a weather change or similar, the mobile deviceswitches path to follow the second path calculated locally at the mobile device.

Action. Upon entering or being in a third sub-region having a level of connectivity equal to or above the threshold, the mobile devicemay switch path to follow a third path calculated at the one or more network nodes, over the third sub-region of the region.

Action. Upon not being able to calculate the second path within the second sub-region, the mobile devicemay retrace to a last position where the level of connectivity is equal to or above the threshold.

Action. Upon entering or being in the first sub-region having a level of connectivity above or equal to the threshold, the mobile devicemay download a safe subgraph of a map for the second sub-region. The safe subgraph may comprise one or more possible paths over the second sub-region. A density of path possibilities of the safe subgraph may be based on capability and/or available capacity of the mobile deviceand/or the communication network.

Action. In some embodiments, if the mobile device detects an obstacle in the first sub-region, the mobile devicemay request an updated first path from the one or more network nodes.